fix array symbols in proxies substitution for pull pattern (probably breaks other patterns)

lbmpy/advanced_streaming/indexing.py

@@ -88,10 +88,10 @@ class BetweenTimestepsIndexing:
 
         if (f_dir, inverse) in self._trivial_offset_translations:
             offsets = (0, ) * self._dim
-        else:
-            offset_array_symbols = self._offset_array_symbols(f_dir, inverse)
-            offsets = tuple(sp.IndexedBase(s, shape=(1,))[index] for s in offset_array_symbols)
-            self._required_offset_arrays.add((f_dir, inverse))
+        elif f_dir == 'in':
+            offset_array_symbols = self._offset_array_symbols(f_dir, True)
+            offsets = tuple(sp.IndexedBase(s, shape=(1,))[self.dir_symbol] for s in offset_array_symbols)
+            self._required_offset_arrays.add((f_dir, True))
 
         return {'index': translated_index, 'offsets': offsets}